Collagen, best known as the key protein in skin, also protects against loose bits of plaque that can cause heart attacks. New images (below) of human arteries hardened by plaque illustrate the importance of collagen (green). The plaques (red and orange) in the left two micrographs are stable, while the plaques in the photos on the right are vulnerable to breaking away from the blood vessel wall.
Cells lining blood vessels secrete tiny spheres, called extracellular vesicles, filled with calcium and phosphate. The spheres fuse into calcified plaques (left images) under a protective collagen coating, Harvard Medical School’s Joshua Hutcheson and colleagues report January 11 in Nature Materials. The plaque poses little risk if the collagen layer isn’t disturbed. But when immune cells called macrophages invade the area to clear out infections or heal wounds, they can secrete chemicals that break down collagen and poke holes in the safety net. As a result, the vesicles clump into smaller, less stable plaques (right images).
Studying how arteries harden may lead to therapies that stabilize plaques and eventually dissolve them or prevent them from building up in the first place.
View of a vessel
Two sections of a human artery (center) imaged in a recent study have different arrangements of plaque deposited along the wall. The section at left is relatively stable, with a layer of collagen (green) protecting the plaque (red). At right, small clumps of collagen-covered plaque have formed, leaving them vulnerable to breaking away.